Figure 4

Line profiles of (a) 0 nm (b) 15 nm (c) 30 nm of NaF and potential distribution (d) 0 nm (e) 15 nm (f) 30 nm of NaF with CZTSSe thin-films. Line profiles along the topographic image and the surface potential as indicated red line in Figures 3. The CZTSSe thin-film with NaF shows positively charged potential of the fully GB region.